A Combined Approach Using Patch-Clamp Study ... - Semantic Scholar

Current Cardiology Reviews, 2008, 4, 244-250

244

A Combined Approach Using Patch-Clamp Study and Computer Simulation Study for Understanding Long QT Syndrome and TdP in Women Tetsushi Furukawa1,*, Junko Kurokawa1 and Colleen E. Clancy2 1

Department of Bio-Informational Pharmacology, Madical Research Institute, Tokyo Medical and Dental University; Department of Physiology and Biophysics, Institute for Computational Biomedicine, Weill Medical College of Cornell University 2

Abstract: Female sex is an independent risk factor for development of torsade de pointes (TdP)-type arrhythmias in both congenital and acquired long QT syndrome (LQTS). In females, QTc interval and TdP risk vary during the menstrual cycle and around delivery. Biological experiments including single-cell current recordings with the patch-clamp technique and biochemical experiments show that progesterone modulates cardiac K+ current and Ca2+ current via the non-genomic pathway of the progesterone receptor, and thus the cardiac repolarization duration, in a concentration-dependent manner. Incorporation of these biological findings into a computer model of single-cell and coupled-cell cardiomyocytes simulates fluctuations in QTc interval during the menstrual cycle with reasonable accuracy. Based on this model, progesterone is predicted to have protective effects against sympathetic nervous system-induced arrhythmias in congenital LQTS and drug-induced TdP in acquired LQTS. A combined biological and computational approach may provide a powerful means to risk stratify TdP risk in women.

Key Words: Long QT syndrome, sex hormone, nitric oxide, arrhythmia, patch-clamp, non-genomic pathway INTRODUCTION A growing body of evidence suggests that clinical arrhythmia syndromes emerge as a result of complicated interactions of multiple endogenous and environmental factors. A combined approach using patch-clamp study and computer simulation study is a powerful means for investigating the influence of multiple interacting factors on the development of clinical symptoms. In this mini-review, we will discuss our recent work using a combined biological and computational approach to predict arrhythmic risks in women. 1. ARRHYTHMIAS IN LONG QT SYNDROME (LQTS) IN WOMEN LQTS is a cardiac arrhythmia syndrome characterized by prolonged QT intervals on the 12-lead surface electrocardiogram, polymorphic ventricular tachyarrhythmias with unique morphology, called torsade de pointes (TdP), and syncope and sudden death. Experiments using multicellular wedge prepatnion indicate that TdP is triggered by early afterdepolarization (EAD) followed by intramural phase 2 reentry, which is based on hetelogeneous prolongation myocardial action potential duration (APD) [3]. APD prolongation is caused by either suppression of outward currents including transient outward current (Ito), and rapidly-activating and slowly-activating delayed rectifier K+ current (IKs and IKr), or/and enhancement of inward currents including L-type Ca2+ current (ICa,L) and persistent Na+ current (INa). LQTS occurs as a congenital form or an acquired form. In both congenital and acquired LQTS, female sex is an independent risk factor for the development of TdP [1, 2]. In *Address correspondence to this author at the Department of Bioinformational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University; E-mail: [email protected] 1573-403X/08 $55.00+.00

females, there are dynamic fluctuations in QTc interval and the risk of TdP during the menstrual cycle [4]. Although several previous studies did not find QTc interval differences among the different menstrual phases [5, 6], a recent study analyzing various parameters of cardiac repolarization finds that repolarization duration is shorter in the luteal phase than in the follicular phase by about 10 msec [6]. Ibutilide is a class III antiarrhythmic agent that prolongs QTc interval in a dose-dependent manner, and is used for termination of atrial fibrillation and atrial flutter. QTc prolongation induced by ibutilide is the greatest during menses (63 msec), intermediate in ovulation (59 msec), and the least in the luteal phase (53 msec) [5]. In these studies [5, 7], serum sex hormone level was determined: serum progesterone level was higher in the luteal phase than in the follicular phase, during menses, and in ovulation, while serum 17-estradiol level was not significantly different between the luteal phase and the follicular phase. Thus, progesterone is suggested to be responsible for differences in cardiac repolarization duration and in ibutilide-induced QTc prolongation during the menstrual cycle. In post-menopausal women, although earlier studies report conflicting data for effects of hormone replacement therapy on QTc interval [8-10]. a recent study consisting of a large study population indicates that hormone replacement therapy with estrogen alone causes slight but significant prolongation of QTc interval by about 2 msec, while combinational hormone replacement therapy with estrogen and progestin consistently shortens QTc interval by about 1 msec [11]. Effects of pregnancy in LQTS patients were also examined [12, 13]. In careful survey of arrhythmia events in congenital LQTS patients around delivery, new-onset of arrhythmia events increased postpartum where progesterone level falls dramatically compared to before or during pregnancy [12]. Taken together, the luteal hormone, progester©2008 Bentham Science Publishers Ltd.

A Combined Approach Using Patch-Clamp Study

Current Cardiology Reviews, 2008, Vol. 4, No. 4

245

one, is strongly suggested to have protective effects against long QT-associated arrhythmias.

3. NON-GENOMIC EFFECTS OF PROGESTERONE ON CARDIAC ION CURRENTS

2. GENOMIC EFFECTS OF PROGESTERONE ON CARDIAC ION CHANNELS

Major currents determining cardiac repolarizaion are IKs, IKr, and ICa,L in human and guinea-pig. Ito and ICa,L are critical in mouse and rat [27, 28]. Thus, we used cardiac myocytes isolated from guinea pig left ventricle to investigate acute effects of progesterone. Sympathetic nervous system (SNS) stimulation is a critical triggering factor for TdP in LQTS patients [29], and thus we examined both the basal condition and the SNS stimulation-mimicked condition with isoproterenol application or with intracellular dialysis of cAMP and okadaic acid (OA). Progesterone at a concentration of 100 nM shortened APD both in the basal condition and the SNSstimulated condition.29 Progesterone-induced APD shortening is via the non-genomic pathway, since progesteroneinduced APD shortening was observed within a few minutes, reached steady-state within 10 min, and was inhibited by a specific progesterone receptor inhibitor, mifepristone (1 M).

Progesterone belongs to lipophilic gonadal steroid hormone family, whose canonical pathway is to permeate into cell across surface membrane, binds to intracellular receptor, translocates into the nucleus as a ligand/receptor complex form, and binds to a gene containing a hormone responsive element (Fig. 1) [14-16]. In addition to this “genomic action”, for the last decade sex hormones have been shown to exhibit rapid actions which cannot be explained by genomic action and are referred to as “non-genomic action” (Fig. 1) [17-20]. Non-genomic action takes place in a membranedelimited manner: PI3-kinase/Akt-dependent activation of endothelial nitric oxide synthase (eNOS) [21, 22] and activation of MAP-kinase [23, 24] are the two most well characterized signaling pathways. Previous studies of effects of progesterone on cardiac ion channels have mostly dealt with its genomic actions. Song et al. [25] examined effects of gonadal steroids on expression of transient outward current channels, KV4.3, using a myometrium heterologous expression as a model system. They found that 4 days-injection of 17-estradiol (50 g/ml) decreased expression of KV4.3, whereas injection of progesterone (3 mg/ml) did not affect KV4.3 expression. The 1C subunit of the L-type Ca2+ current (ICa,L) channel can be detected as a 240 kDa long form (1C long) and a 190 kDa short form (1C short). In myometrium, 17-estradiol decreased the long 1C form/short 1C form (L/S ratio), while progesterone increased the L/S ratio; in brain or heart, either 17-estradiol or progesterone did not change the L/S ratio [26]. Thus, the genomic effects of progesterone on cardiac repolarization are currently undefined and cannot explain a protective effect of progesterone against TdP risk.

The ionic mechanism underlying APD shortening by progesterone is to modulate IKs and ICa,L, but not I Kr. In the basal condition, progesterone enhanced IKs in a concentration-dependent manner with an EC50 value of 2.7 nM, while progesterone did not significantly affect ICa,L (Fig. 2A) [30]. SNS-stimulation caused enhancement of both ICa,L and IKs. Further application of progesterone reduced ICa,L to the level before cAMP and OA application, while it did not significantly change IKs [30]. The IC50 value for ICa,L suppression was 29.9 nM (Fig. 2B). The biophysical mechanism for regulation of IKs and ICa,L is different. The effects of progesterone on IKs were frequency- and voltage-independent [30]. In contrast, progesterone caused a positive shift in the ICa,L activation curve and a negative shift in the inactivation curve [30]. Computer simulation analysis showed that changes in current conduc-

Fig. (1). Genomic and non-genomic pathway of sex hormones. In the genomic pathway, sex steroid hormones penetrate into cells, and bind to receptors in the cytosol. The ligand/receptor complex then translocates into the nucleus, binds to the genes with hormone responsive element (HRE), and regulates gene expression. In the non-genomic pathway, sex hormones release nitric oxide via the PI3-kinase/Akt/eNOS pathway or activate MAP-kinase in a membrane-delimited manner.

246 Current Cardiology Reviews, 2008, Vol. 4, No. 4

Furukawa et al.

Fig. (2). Two distinct mechanisms for NO actions. NO activates sGC, and produced cGMP regulates PKG, PDE2, PDE3, and/or protein phosphatase (PPase). NO also induces protein snitrosylation. ICa,L suppression by progesterone is via the sGC/cGMP pathway, while IKs activation is via the protein s-nitrosylation. Inset shows the antagonistic action between cAMP and cGMP for ICa,L regulation. It has been reported that in rabbit and frog ventricular myocytes, it occurs at the PDE2 level, while in guinea-pig and rat ventricular myocytes, it occurs at the PKG level [34]. The inhibition of PDE3 by cGMP and the activation of PPase by cGMP/PKG signaling pathway may also be involved.

tance without changes in current kinetics reproduced the effects of progesterone on IKs observed in biological experiments. Changes in voltage dependency alone with no change in current conductance reproduced the effects of progesterone on ICa,L with a high accuracy. Thus, effects of progesterone on IKs are mainly to alter current conductance and modulate ICa,L by affecting current kinetics. Despite distinct biophysical mechanism for I Ks and ICa,L regulation, the principal mediator for both IKs enhancement in the basal condition and ICa,L suppression in the SNSstimulated condition appears to be nitric oxide (NO), since both were abolished by nitric oxide (NO) trappers and eNOS inhibitors [31, 32]. However, the mechanism by which NO modulates IKs and ICa,L appears to be different. ICa,L suppression by progesterone was abolished by an inhibitor of soluble guanylyl cyclase (sGC), indicating that ICa,L is regulated by progesterone via a NO/sGC/cGMP axis (Fig. 3) [33]. Antagonistic action of cAMP and cGMP for ICa,L has been demonstrated, which appears to vary among species [34]. In rabbit and frog ventricular myocytes, cGMP antagonizes cAMP effects by promoting cAMP breakdown by activating cGMPdependent phosphodiesterase (PDE2) [34]. In guinea-pig and rat ventricular myocytes, cAMP-dependent protein kinase (PKA) phosphorylates the -subunit of ICa,L and enhances ICa,L only in the presence of A-kinase anchoring protein (AKAP) [34]. cGMP-dependent protein kinase (PKG) phosphorylates both the -subunit and the -subunit of ICa,L [35]. Phosphorylation of the -subunit by PKG does not affect ICa,L, likely due to the absence of AKAP, while phosphorylation of the -subunit antagonizes the effect of the -subunit phosphorylation by PKA [35]. In addition, the inhibition of

PDE3 by cGMP to enhance the cAMP-induced activation and facilitation of ICa,L, and activation of protein phosphatase via cGMP-PKG signaling pathway to suppress the cAMPmediated facilitation may contribute to the complicated interaction of cAMP and cGMP in the heart. On the other hand, IKs enhancement was not inhibited by a sGC inhibitor, but was inhibited by a thiol-alkylating reagent, N-ethylmaleimide, and a reducing reagent, di-thiothreitol [33]. These data suggest that cGMP-independent mechanisms, possibly protein s-nitrosylation, play a role for IKs enhancement (Fig. 3) [33]. Protein s-nitrosylation is the direct NO transfer to the thiol residue of Cys, is highlighted as a novel mechanism of protein post-translational modification [36, 37], and occurs independent of cAMP. Thus, it is possible that progesterone regulates IKs in the basal condition and ICa,L only in the SNS-stimulated condition. However, it remains to be proven if the IKs channel is indeed s-nitrosylated. If that is the case, it is also undetermined whether the -subunit, KCNQ1, or the -subunit, KCNE1, is the target of s-nitrosylation, what is the underlying mechanism for specific s-nitrosylation of KCNQ1 or KCNE1, and how snitrosylation induces IKs channel activation. 4. COMPUTATIONAL SIMULATION OF THE EFFECTS OF PROGESTERONE QTc interval and TdP risk are regulated by various factors, including SNS status, heart rate, medications, serum electrolyte level, and others. Our biological experiments suggest progesterone as an additional major factor that modulates QTc interval and TdP risk. Since progesterone



247

Fig. (3). Non-genomic regulation of IKs and ICa,L by progesterone in patch-clamp experiments. A) In the basal condition, progesterone (P4) enhances IKs. a, Representative superimposed IKs current traces in the control and after treatment with 100 nM P4. IKs was elicited by depolarization to +50 mV from a holding potential of -40 mV at 0.1 Hz. b, Concentration-response curve for IKs enhancement by progesterone. EC50 was 2.6 nM. B) In the SNS-stimulation-mimicked condition, progesterone suppressed ICa,L. a, Representative superimposed ICa,L current traces in the control, during intracellular dialysis of cAMP and OA, and after treatment with 100 nM P4 in the continued presence of cAMP and OA. ICa,L was elicited by depolarization from a holding potential of -40 mV to 0 mV at 0.1 Hz. b, Concentration-response curve for ICa,L suppression by progesterone. IC50 was 29.9 nM.

level varies during the menstrual cycle and around delivery, progesterone effects may contribute to the fluctuation of QTc interval and TdP risk during the menstrual cycle and pregnancy. Since a computational approach is especially powerful to simulate these changes, our first challenge was to investigate if incorporating effects of progesterone in the cardiac APD computer model reproduces fluctuation of APD during the menstrual cycle. We incorporated effects of progesterone obtained in our biological experiments in the Faber-Rudy model of the guinea pig myocyte [38]. Since reported progesterone level in women is ~2.5 nM in the follicular phase and ~40.6 nM in the luteal phase [39], we incorporated effects of progesterone at 2.5 nM and at 40.6 nM. The model predicts that progesterone at 40.6 nM shortens APD by 3.7 % under basal conditions and 4.6 % under SNS-stimulated conditions compared to APD at 2.5 nM progesterone (Fig. 4) [30]. Clinically observed QT intervals are shorter by about 2.4%-2.8 % in the luteal phase than in follicular phase [5], and so the APD shortening predicted in the model (3.7-4.6 %) fits well with the observed fluctuation in QT interval during the menstrual cycle in women. Effects of progesterone in a single cell do not necessarily predict the effect at the multi-cell level, organ level, or in vivo level. As a first step to simulate effects of progesterone in higher dimensions, we constructed a coupled-cells model, in which 100 cardiomyocytes are electrotonically connected

with simulated resistances between them to represent gapjunctions. We then investigated the effects of progesterone and SNS in simulated coupled tissue and computed virtual electrograms from simulated gradients of depolarization and repolarization. Simulations suggest that during the luteal phase when progesterone = 40.6 nM, maximal SNS may additionally shorten QT interval by 12.2 % (Fig. 4) [30]. These simulations support the notion that progesterone may exert protective QT shortening effects under conditions on SNS. 5. PREDICTED EFFECTS OF PROGESTERONE AGAINST ARRHYTHMIA Since the model reproduces the effects of progesterone on APD in patch-clamp experiments and QTc variation during the menstrual cycle in women with a good accuracy, our next step was to utilize this model to predict the effects of progesterone on LQTS-associated arrhythmia susceptibility. To examine the effects on SNS-induced arrhythmias, we used the D76N KCNE1 mutation linked to congenital LQTS5. I Ks exhibits accumulation in the pre-open state during the rapid heart rates, resulting in action potential adaptation [40]. SNS stimulation enhances ICa,L to increase Ca2+ influx [41]. SNS stimulation also enhances IKs [42, 43] that counter-balances ICa,L enhancement and maintains APD within a certain range [44]. In LQTS1 and LQTS5, I Ks channel disturbance results in dysfunction of action potential adaptation to rapid heart rates and response to SNS stimulation.

248 Current Cardiology Reviews, 2008, Vol. 4, No. 4

Furukawa et al.

Fig. (4). The effects of progesterone on simulated cardiac action potentials. A) Simulated action potentials in the absence (a) and presence (b) of simulated SNS stimulation under baseline conditions (dashed line) and with 2.5 nM (solid line) and 40.6 nM (dashed-dot-dot line) progesterone. The 10th paced beat at a pacing interval of 400 ms is shown. B) Left panel: Simulated action potentials (10th paced beat at a 400 ms pacing interval) in a 1 cm cardiac fiber (cell number=100; top is cell #1, and bottom is cell #100). An action potential was elicited at cell #1, and propagated from top to bottom. a, Baseline (no SNS stimulation and no progesterone). b, With 40.6 nM progesterone. c, With 40.6 nM progesterone in the presence of SNS stimulation. Right panel: Computed virtual electrograms under the three conditions. The corresponding T-waves are indicated with arrows.

The D76N KCNE1 mutation reduces the current and renders the I Ks channel insensitive to adrenergic stimulation [45], thus probands carrying D76N KCNE1 mutation readily develop TdP with SNS stimulation at rapid heart rates [46]. In the absence of progesterone, the mutant model cells are unable to adapt to the fast pacing frequency because I Ks fails to increase in response to the SNS stimulation (Fig. 5A) [30]. Interestingly, both in the single-cell and coupled-cell model in the presence of progesterone at 2.5 nM, some improvement is observed; in the presence of 40.6 nM, a failed SNS stimulation response is compensated for by the action of progesterone alone to increase IKs (Fig. 5A) [30]. Thus, enhancement of IKs in the absence of SNS stimulation, and inhibition of cAMP-induced ICa,L by progesterone improve action potential adaptation, which is dependent on progesterone level. These simulations suggest a mechanism for SNSrelated arrhythmic risk varies during the menstrual cycle in women. Drug-induced TdP is believed to occur by blockade of the human ether-a-go-go related gene (hERG) channel by drugs with various structures [47], and at slow heart rates. In a simulation, severe EADs were induced by 50% block of IKr at a slow heart rate (30 bpm) (Fig. 5B). At 2.5 nM of progesterone, some improvement is observed (middle panel); at

40.6 nM of progesterone, the EADs are abolished and the action potential morphology is normalized (Fig. 5B). Thus, progesterone is predicted to have protective effects against drug-induced arrhythmias, which also fluctuate during the menstrual cycle. Progesterone does not have apparent effects on IKr (data not shown), and thus predicted protection against drug-induced EAD may be attributed to an increase in repolarization reserve by I Ks enhancement [48]. CONCLUSION Our patch-clamp experiment demonstrates that the nongenomic effect of the sex hormone progesterone constitutes a novel regulatory mechanism of cardiac repolarization. Serum progesterone level fluctuates during the menstrual cycle: within this level, progesterone modulates I Ks and ICa,L and, therefore, is partly responsible for the cyclic changes in QTc interval and TdP risk during the menstrual cycle. A computational approach allows for simulation of multi-factorial and periodical phenomenon. Incorporation of progesterone effects observed in our biological study into the computational model reproduces cyclic changes in QTc interval, and predicts dose-dependent protective effects of progesterone against SNS-stimulation-induced and drug-induced arrhythmias. This approach provides a first step to risk stratify TdP



249

Fig. (5). Progesterone may protect against long QT-related arrhythmia. A) The effects of progesterone on arrhythmic rhythms in congenital LQTS. Progesterone improves action potential adaptation in congenital LQTS (LQTS5) at fast heart rates during SNS stimulation. We simulated the D76N mutation in the IKs -subunit KCNE1 that disrupts regulation of IKs by protein kinase A. Left panel: Shown are 6 action potentials (15th - 20th) elicited from cells with D76N IKs at a fast rate (CL = 150 ms) during the SNS stimulation in the absence (top panel), and in the presence of 2.5 nM (middle panel) or 40.6 nM (bottom panel) progesterone. Right Panel: Simulated propagation of action potentials in paced (150 ms, 29th and 30th beats are shown) one-dimensional tissue in the absence of progesterone (a), in the presence of 40.6 nM progesterone (b) and the corresponding computed electrogram. A gray circle in panel a highlights failure of propagation of the second stimulus, which is applied during the mutation induced extended refractory period. B) The effects of progesterone on EADs resulting from acquired LQTS simulated by IKr block. Traces of the 9th and 10th action potentials during 50% IKr block in the absence (top panel), and in the presence of 2.5 nM (middle panel) or 40.6 nM (bottom panel) progesterone. The cycle length is 2000 ms. The left panel shows the single cells and the right panel shows results in corresponding fibers under the same conditions.

arrhythmias in women. To improve this approach, further efforts are certainly needed, which include the elucidation of; (1) the effects of sex hormones other than progesterone, including various estrogen metabolites; (2) genomic effects of progesterone and estrogens; and (3) simulation at the organ and in vivo level. ACKNOWLEDGEMENTS This work was supported in part by grant-in-aid 17081007 (T.F.) for Scientific Research on Priority Areas, grants 18390231 (T.F.) and 19689006 (J.K.) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan, and a research grant from the Mitsui Kousei Foundation (T.F.) and the Naito Foundation (J.K.). The research was also supported by grants from the American Heart Association, the National Institutes of Health NHLBI RO1-HL085592 and the Alfred P. Sloan Foundation to C.E.C. REFERENCES [1]

[2]

[3] [4]

[5]

Makkar RR, Fromm BS, Steinman RT, Meissner MD, Lehmann MH. Female gender as a risk factor for torsades de pointes associated with cardiovascular drugs. JAMA 1993; 270: 2590-2597. Locati EH, Zareba W, Moss AJ, et al. Age- and sex-related differences in clinical manifestations in patients with congenital long-QT syndrome: findings from the International LQTS Registry. Circulation 1998; 97: 2237-2244. Antzelevitch C, Shimizu W, Yan GX, Sicouri S. Cellular basis for QT dispersion. J Electrocardiol 1998; 30(supple): 168-175. Furukawa T, Kurokawa J. Regulation of cardiac ion channels via non-genomic action of sex steroid hormones: Implication for the gender difference in cardiac arrhythmias. Pharmacol Ther 2007; 115: 106-115. Rodriguez I, Kilborn MJ, Liu XK, Pezzullo JC, Woosley RL. Drug-induced QT prolongation in women during the menstrual cycle. JAMA 2001; 285: 1322-1326.

[6] [7]

[8] [9]

[10] [11]

[12]

[13] [14] [15] [16]

[17] [18]

Hulot JS, Demolis JL, Riviere R, Strabach S, Christin-Maitre S, Funck-Brentano C. Influence of endogenous oestrogens on QT interval duration. Eur Heart J 2003; 24: 1663-1667. Nakagawa M, Ooie T, Takahashi N, et al. Influence of menstrual cycle on QT interval dynamics. Pacing Clin Electrophysiol 2006; 29: 607-613. Larsen JA, Tung RH, Sadananda R, et al. Effects of hormone replacement therapy on QT interval. Am J Cardiol 1998; 82: 993995. Sbarouni E, Zarvalis E, Kyriakides ZS, Kremastinos DT. Absence of effects of short-term estrogen replacement therapy on resting and exertional QT and QTc dispersion in postmenopausal women with coronary artery disease. Pacing Clin Electrophysiol 1998; 21: 2392-2395. Haseroth K, Seyffart K, Wehling M, Christ M. Effects of progestinestrogen replacement therapy on QT-dispersion in postmenopausal women. Internat J Cardiol 2000; 75: 161-165. Kadish AH, Greenland P, Limacher MC, Frishman WH, Daugherty SA, Schwartz JB. Estrogen and progestin use and the QT interval in postmenopausal women. Ann Noninvasive Electrocardiol 2004; 9: 366-374. Rashba EJ, Zareba W, Moss AJ, et al. Influence of pregnancy on the risk for cardiac events in patients with hereditary long QT syndrome. LQTS Investigators. Circulation 1998; 97: 451-456. Heradien MJ, Goosen A, Crotti L, et al. Does pregnancy increase cardiac risk for LQT1 patients with the KCNQ1-A341M mutation? J Am Coll Cardiol 2006; 48: 1410-1415. Beato M, Klug J. Steroid hormone receptors: an update. Hum Reprod Update 2000; 6: 224-236. Aranda A, Pascual A. Nuclear hormone receptors and gene expression. Physiol Rev 2001; 81: 1269-1304. McKenna NJ, O'Malley BW. Nuclear receptors, coregulators, ligand, and selective receptor modulators: making sense of the patchwork quilt. Ann N Y Acad Sci 2001; 949: 3-5. Levin ER. Cellular functions of plasma membrane estrogen receptors. Steroids 2002; 67: 471-475. Losel RM, Falkenstein E, Feuring M, et al. Nongenomic steroid action: controversies, questions, and answer. Physiol Rev 2003; 83: 965-1016.

250 Current Cardiology Reviews, 2008, Vol. 4, No. 4 [19]

[20] [21]

[22]

[23] [24]

[25] [26]

[27] [28] [29]

[30]

[31]

[32]

[33]

Furukawa et al.

Watson CS, Gametchu B. Proteins of multiple classes may participate in nongenomic steroid actions. Exp Biol Med 2003;; 228: 1272-1281. Bai CX, Kurokawa J, Tamagawa M, Nakaya H, Furukawa T. Nontranscriptional regulation of cardiac repolarization currents by testosterone. Circulation 2005; 112: 1701-1710. Simoncini T, Mannella P, Fornari L, Caruso A, Varone G, Genazzani AR. Genomic and non-genomic effects of estrogens on endothelial cells. Steroids 2004; 69: 537-542. Haynes MP, Sinha D, Russell KS, et al. Membrane estrogen receptor engagement activates endothelial nitric oxide synthase via the PI3-kinase-Akt pathway in human endothelial cells. Circ Res 2000; 87: 677-682. Endoh H, Sasaki H, Maruyama K, et al. Rapid activation of MAP kinase by estrogen in the bone cell line. Biochem Biophys Res Commun 1997; 235: 99-102. Watters JJ, Campbell JS, Cunningham MJ, Krebs EG, Dorsa D. Rapid membrane effects of steroids in neuroblastoma cells: effects of estrogen on mitogen activated protein kinase signalling cascade and c-fos immediate early gene transcription. Endocrinology 1997; 138: 4030-4033. Song M, Helguera G, Eghbali M, et al. Remodeling of KV4.3 potassium channel gene expression under the control of sex hormones. J Biol Chem 2001; 276: 31883-31890. Helguera G, Olcese R, Song M, Toro L, Stefani E. Tissue-specific regulation of Ca2+ channel protein expression by sex hormones. Biochim Biophys Acta 2002; 1569: 59-66. Varró A, Lathrop DA, Hester SB, Nánásai OO, Papp JG. Ionic currents and action potentials in rabbit, rat and guinea pig ventricular myocytes. Basic Res Cardiol 1993; 88: 93-102. Furukawa T, Kurokawa J. Potassium channel remodeling in cardiac hypertrophy. J Mol Cell Cardiol 2006; 41: 753-761. Schwartz PJ, Priori SG, Cerrone M, et al. Left cardiac sympathetic denervation in the management of high-risk patients affected by the long-QT syndrome. Circulation 2004; 109: 1826-1833. Nakamura H, Kurokawa J, Bai C-X, et al. Progesterone regulates cardiac repolarization through a nongenomic pathway. An in vitro patch-clamp and computational modeling study. Circulation 2007; 116: 2913-2922. Bai CX, Namekata I, Kurokawa J, Tanaka H, Shigenobu K, Furukawa T. Role of nitric oxide in Ca2+-sensitivity of the slowly activating delayed rectifier K+ current in cardiac myocytes. Circ Res 2005; 96: 64-72. Bai CX, Takahashi K, Masumiya H, Sawanobori T, Furukawa T. Nitric oxide-dependent modulation of the delayed rectifier K+ current and the L-type Ca2+ current by ginsenoside Re, an ingredient of Panax ginseng, in guinea-pig cardiomyocytes. Brit J Pharmacol 2004; 142: 567-575. Furukawa T, Bai C-X, Kaihara A, et al. Ginsenoside Re, a main phytosterol of Panax ginseng, activates cardiac potassium channels

Received: 17 April, 2008

Revised: 31 May, 2008

Accepted: 31 May, 2008

[34]

[35]

[36] [37] [38]

[39]

[40]

[41] [42] [43]

[44]

[45] [46]

[47] [48]

via a nongenomic pathway of sex hormones. Mol Pharmacol 2006; 70: 1916-1924. Fischmeister R, Castro L, Abi-Gerges A, Rochais F, Vandecasteele G. Species- and tissue-dependent effects of NO and cyclic GMP on cardiac ion channels. Comp Biochem Physiol - Part A: Mol Integ Physiol 2005; 142: 136-143. Yang L, Liu G, Zakharov SI, Bellinger AM, Mongillo M, Marx SO. Protein kinase G phosphorylates Cav1.2 1c and 2 subunits. Circ Res 2007; 101: 465-474. Hess DT, Matsumoto A, Nudelman R, Stamler JS. S-nitrosylation: spectrum and specificity. Nat Cell Biol 2001; 3: E46-E49 Hess DT, Matsumoto A, Kim SO, Marshall HE, Stamler JS. Protein S-nitrosylation: purview and parameters. Nat Rev 2005; 6: 150-166. Faber GM, Rudy Y. Action potential and contractility changes in [Na+]i overloaded cardiac myocytes: a simulation study. Biophys J 2000; 78: 2392-2404. Janse de Jonge XA, Boot CR, Thom JM, Ruell PA, Thompson MW. The influence of menstrual cycle phase on skeletal muscle contractile characteristics in humans. J Physiol (Lond) 2001; 530: 161-166. Clancy CE, Kurokawa J, Tateyama M, Wehrens XH, Kass RS. K+ channel structure-activity relationships and mechanisms of druginduced QT prolongation. Annu Rev Pharmacol Toxicol 2003; 43: 441-461. Reuter H. Calcium channel modulation by neurotransmitters, enzymes and drugs. Nature 1983; 301: 569-574. Walsh KB, Kass RS. Regulation of a heart potassium channel by protein kinase A and C. Science 1988; 242: 67-69. Marx SO, Kurokawa J, Reiken S, et al. Requirement of a macromolecular signaling complex for beta adrenergic receptor modulation of the KCNQ1-KCNE1 potassium channel. Science 2002; 295: 496-499. Terrenoire C, Clancy CE, Cormier JW, Sampson KJ, Kass RS. Autonomic control of cardiac action potentials: role of potassium channel kinetics in response to sympathetic stimulation. Circ Res 2005; 96: e25-34. Kurokawa J, Chen L, Kass RS. Requirement of subunit expression for cAMP-mediated regulation of a heart potassium channel. Proc Natl Acad Sci USA 2003; 100: 2122-2127. Splawski I, Tristani-Firouzi M, Lehmann MH, Sanguinetti MC, Keating MT. Mutations in the hminK gene cause long QT syndrome and suppress IKs function. Nat Genet 1997; 17: 338-340. Sanguinetti MC, Mitcheson JS. Predicting drug-hERG channel interactions that cause acquired long QT syndrome. Trends Pharmacol Sci 2005; 26: 119-124. Roden DM. Long QT syndrome: reduced repolarization reserve and the genetic link. J Internat Med 2006; 259: 59-69.